historicafandomcom-20200222-history
Behavioral genetics
Behavioral genetics is a major field of genetics which studies the nature and origins of individual differences in behavior, relying on statistics to gain insight into the difference between nature and nurture, and the genetics behind unusual traits. History Studies Behavioral genetics is an incredibly difficult field of study which seeks to determine the degree upon which a behavioral trait is influenced by genetics. It is hard to do controlled experiments in human populations, so research relies heavily on inbred animal studies and twin studies for the data that is interpreted. In inbred animal studies, scientists can create a strain of mice that is genetically highly inbred, making them homozygous at almost all their loci. Researchers can also do behavioral experiments to determine how these inbred animals respond to different situations such as maze running. Maze running can show how inbred mice run a learning maze, and scientists can breed fast-running mice and slow-running mice by selective breeding, in addition to determining the degree of "heritability" (the portion of the variance that is the contribution of genetics to the trait). Heritability ranges from 1 (totally influenced by genetics) to 0 (totally influenced by the environment). Interestingly, separated twins often have remarkably similar IQs, disease risks, behavioral trait risks, favorite colors, and other traits, showing high heritability. As twins mature, the controls over the actual expression of the genes they inherit can change over time. Environmental influences like diet and smoking can alter gene expression a great deal, and this can have a significant effect on the phenotypes of even monozygotic twins. Essentially, genes are not destiny, as there are several natural modifications which can occur. Most studies up until the late 1980s concluded that nurture and environment was the main influence on gender identity, and that homosexuality was a choice which could be corrected with therapy. The thinking was so prevalent that in the cases of ambiguous genitalia, surgery could be done to make a genetically XY male an anatomic female via surgery; it was believed that the gender identity of a normal female could be accomplished after surgery via therapy. John Money, a Johns Hopkins University professor and leading expert on gender identity, came across a Canadian identical twin, David Reimer, whose genitalia was injured during circumcision. The doctors recommended for Reimer to be surgically reconstructed as a female, and he went through the process. During his teenage years, Reimer rebelled against being raised as a female, as he felt that his gender identity was that of a male. Money saw the female gender development as successful at first, but David shot himself in 2004, two years after his brother's overdose; the family blamed Money's philosophy for their sons' deaths. No one has created as much controversy in scientific literature as the debate over a genetic versus an environmental (cultural) cause to homosexuality. Evidence for the important role of parrents on the sexual orientation of their children is abundant in the literature-classic Freudian explanation of having an overprotective mother and a distant father. Evidence also exists for a possible genetic role in this sexual orientation. Dean Hamer mapped a gene for homosexuality on the X chromosome, whime Simon LeVay showed differences in the brain anatomy of gay men that was similar to the changes seen in females and different from that seen in non-gay men (smaller size of an area in the hypothalamus in gay men), using the brains of deceased AIDS patients of both sexual orientations. Twin studies, in terms of concordance rates, are of great interest to scientists. They look at a behavioral trait in monozygotic twins, especially when the twin pairs are raised apart. Concordance among monozygotic twins for homosexualitity has been estimated to be as high as 54% and as low as 24%, depending on the study cited. Homosexual monozygotic twins have about two times the concordance rate compare to dyzygotic twins. Transsexuality is a condition in which a person relates to, or is a person whose gender identity is opposie the sex the person had or was identified as having at birth. Transsexual people may or may not undergo surgery and the hormone therapy to obtain a physical appearance typical of the gender they identify as. Biologically, transsexual people feel a need to alter their gender role, and they can go through surgery or hormonal therapy. Category:Genetics Category:Psychology